The invention relates to a girder for the production of a track for track-bound vehicles, in particular a magnetic levitation railway, with a heat-insulating cover mounted at its upper side and to a track produced therewith.
Girders and tracks of this type are widely known (e.g. DE 39 28 277 C1, DE 39 28 278 C2). They serve for tracking and accommodation of functional components and/or equipment parts such as stator packs, lateral guide rails, and sliding tracks which act together with relevant functional components mounted at the vehicle, for example carrier, exciter, brake and guide magnets as well as carrier skids or similar components.
The girders can be made of steel or concrete and be configured as single-span or multispan girders. To allow for thermal expansion they are supported by the aid of fixed or movable bearings on columns or on a substructure erected on the ground (e.g. DE 34 04 061 C1). Single-span girders are supported at one end by means of a fixed bearing and at the other end by means of a movable bearing, while two-span girders are supported by means of a movable bearing each at both ends and in the middle area by means of a fixed bearing. Girders comprised of more than two spans, e.g. like those applied in the area of turnouts, are equipped, in addition to the end-side movable bearings, with two or more bearings that permit thermal expansion in horizontal direction, but largely prevent vertical movement. For example, the practical construction lengths for two-span girders amount to 30 m to 60 m, while these lengths amount to roughly half that value for single-span girders.
Girders of the type described herein above can bend convexly if subjected to the influence of temperature fluctuations, particularly vertically to their longitudinal direction. While the top and bottom chords of these girders assume the same temperature if warmed-up evenly and simultaneously, thus expanding and/or contracting nearly evenly in longitudinal direction, girders get bent, for example if subjected to solar radiation, because the top chords get warmed-up faster than the bottom chords if subjected to solar radiation, and thus they are expanded stronger than the bottom chords. With single-span girders a bending-up of this type vertically to the girder longitudinal axes takes place with a much higher, approx. three times higher amplitude than that for two-span and multispan girders, because a deformation practically cannot occur in the area of the central fixed bearing.
Deformations of this type as described hereinabove lead to a waving of the track, thus affecting travel comfort. Even a safe and secure tracking and, in case of a magnetic levitation track, the contactless levitation may be endangered by too serious a deformation. Therefore, to avoid such problems, it is common practice to use only two-span and multispan girders, putting up with those disadvantages in view of production, transport, and assembly resulting from the increased construction size and heavier weight.
To reduce the deformation of the girders, it had already been proposed to mount a heat-insulating cover made of polystyrene high-resistance foam on their upper side and a protective layer made of glass fiber concrete on top of it. However, tests run for this purpose were stopped, because it is difficult to achieve sufficient fatigue strength for such covers. In particular, during the usual operation of a track produced with such girders, high transverse and shearing stresses affecting the fatigue strength develop due to the different thermal expansion of the girder material as compared with the material of the covers on the one hand and due to the different types of coating on the other hand.
In contrast therewith, it is the task of this invention to provide a heat-insulating cover that is stable and durable, withstanding those strains and stresses occurring during track operation in the event of strong solar radiation.
According to the invention, a girder for the production of a track for track-bound vehicles, in particular a magnetic levitation railway is provided with a heat-insulating cover mounted at an upper side. The cover rests on a floating bearing.
According to another aspect of the invention, a track for track-bound vehicles, in particular for a magnetic levitation railway has a plurality of girders arranged one behind another in the direction of travel. At least selected girders are configured with a heat-insulating cover mounted at an upper side. The cover rests on a floating bearing.
The invention bears the advantage that the heat-insulating covers, because of their floating support, do not belong to the stability system of the girders. Thus, stresses in the cover due to different coefficients of expansion are minimized. Therefore, plates consisting of high-grade materials, e.g. solar cell modules, serving for additional purposes, can also be used for these covers. In particular, it brings the advantage that due to the effective and durable heat insulation, it is possible to ensure so little temperature differences between the top and bottom chords permanently, even in the event of strong solar radiation, that single-span girders will not get more deformed than appropriately sized two-span or multispan girders.
The cover may be formed by a plurality of insulating elements, each of them resting on a floating bearing of their own. The insulating elements may be fixed with collars made of an elastic material at their surface. The collars may consist of a rubber-like material. The collars may be fixed by the aid of clamping rails at the girder upper side. The insulating elements may be at least partly provided with photovoltaic solar cells.
A cavity that is continuous in the direction of travel may be provided under the cover.
The girder may be provided on its upper side with laterally mounted functional components in the form of gliding tracks. The cover may be arranged between the gliding tracks.
A top chord may be arranged between the gliding tracks, forming a bottom of the cavity. The top chord may feature a deepening between the gliding tracks destined for the formation of the cavity. The selected girders may be configured as single-span girders. The cavity may be utilized for the accommodation of lines and cables.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.